A variety of functions have recently been provided in a portable device such as a cellular phone or a smartphone. Particularly, since the portable device is equipped with a built-in digital camera, it may take a picture at any time in any place, and store the picture or transmit the picture to an Internet server or a portable device of another user. Further, the portable device may receive various types of content such as text, images, and videos through a mobile communication network, a wireless Internet, or a short-range communication network, and store the received content. When a user wants the content, the portable device may display the content through its display device. Further, as a camera with a higher resolution and more functions is available in the portable device, the portable device satisfies the user as much as a conventional digital camera.
With the portable device having the digital camera, the user may display and view a captured image on a screen at any time. Meanwhile, the user may need to print the image on a photographic paper, rather than to display it on a screen. In order to print a captured picture on a photographic paper, although inconvenient, the user should provide a picture file stored in the portable device to a printing shop and get the printing shop to deliver a printed picture to the user, or the user should visit a printing shop and pick up a printed picture at the printing shop in person.
Recently, photo printers for printing a portable-size picture, such as “LG Pocket Photo®” of LG Electronics and “Polaroid® GL 10” of Polaroid, have been commercialized. However, such a conventional photo printer requires multiple electronic parts including a communication device for communicating with a computer or a portable device, a memory for storing a received photo file, a processor for providing overall control to the printer, and a battery built inside the printer. Additionally, the conventional photo printer needs an ink or a heat transfer device for forming an image on a photographic paper according to the type of the photographic paper. Due to the use of a lot of internal parts, a manufacturing process of the conventional portable photo printer is complex. Due to its large size and great weight, the conventional photo printer is inconvenient to carry. Particularly because the conventional photo printer requires expensive internal electronic parts, the complete product is expensive, which makes it difficult to be widely used.